Pressure loaded pump



Dec. 5, 1961 D. s. OLIVER PRESSURE LOADED PUMP Filed Nov. 6, 1957 w. wnQMMT m M a 5 8 m n N am u. e fig a J J N N MN j & //V// //V UnitedStates Patent 3,011,448 PRESSURE LOADED PUMP Delbert S. Oliver, Wooster,Ohio, assignor to Borg-Warner Corporation, Chicago, 111., a corp-orationof Illinois Filed Nov. 6, 1957, Ser. No. 694,820 11 Claims. (Cl.103-126) This invention relates to a high pressure gear-type pump orfluid motor and more particularly to an arrangement for maintainingaxially adjustable end plates or bushings in sealing relation with therotatable gears and providing a pumping seal therewith.

In normally constructed pressure loaded gear-type pumps at least onepair of end plates or bushings therein, adjacent to a pair ofintermeshing rotatable gears, are adapted to be axially movable withrespect to the adjacent side faces of the gears whereby the front facesof the end plates engage the side faces of the rotatable gears toprovide a pumping seal therewith. As disclosed in United States PatentNo. 2,420,622 to Roth et al., the axially movable end plates or bushingshave back face portions formed thereon which are spaced from theadjacent end wall, thereby providing a chamber between the axiallymovable end plates and the adjacent end wall. This chamber isinterconnected with the outlet pressure fluid delivered by the rotatedgears, whereby a portion of the outlet pressure fluid is communicated tothe end plate chamber. The force of the pressure fluid present in theend plate chamber acting against the back face portions of the endplates causes movement of the end plates axially toward the rotatablegears, thereby providing a pump seal therewith in opposition to theforce of the pressure fluid acting on the front faces of the end plates,the force of the pressure fluid acting on the front faces being createdby the fluid carried from the inlet to the outlet by the rotating gears.

It has been found that a pressure gradient condition exists within thepumping chamber whereby the pressure value of the fluid passingtherethrough increases from the inlet to the outlet. The force of thepressure fluid existing across the front faces of the end plates tendingto axially move the end plates away from the adjacent side faces of therotatable gears may be balanced or overcome by the force of the pressurefluid in the chamber behind the end plates tending to axially move theend plates toward the gears, thereby maintaining the pumping seal.However, due to the previously mentioned pressure gradient conditionexisting in the pump chamber, the force of the pressure fluid acting onportions of the front faces of the end plates nearer the inlet sidethereof is smaller in magnitude than the force of the pressure fluidacting on portions of the front faces adjacent or nearer the outlet sidethereof. Since the force of the pressure fluid in the chamber behind theend plates acting on the back face portions of the end plates isconstant in magnitude throughout different portions of area thereof, theforce of the pressure fluid acting on the back face portions nearer theinlet side of the end plates is substantially greater in magnitude thanthe magnitude of the force of the pressure fluid acting on the frontfaces in the same region, whereas a much smaller differential inmagnitude of force exists between the opposing forces acting on the endplates in the regions thereof adjacentthe outlet side. This unbalancedcondition causes skewing or twisting of the end plates about the axes ofthe rotatable gears toward the inlet side of the gears and results inuneven wear on the inlet side of the front faces of the end plates.

Many means have been found to substantially compensate for thisunbalanced feature of pressure loaded end plates or bushingsresultingfrom the pressure gradient condition existing across the frontfaces of the end plates. One such means is to provide separate isolatedice 2 chambers between the back faces of the end plates and the adjacentend wall which are subject to pressurized fluids of different pressurevalues whereby the pressure fluid of the lesser pressure value iscommunicated to the chamber adjacent the inlet side and the pressurefluid of the higher pressure value to the chamber adjacent the outlet.It has also been proposed to provide off-set back face surfaces wherebythe majority of the effective area of the back face surfaces is locatedadjacent the outlet side of the end plates. The latter structure-isdisclosed in Haberland application, Serial No. 130,904 filed December 3,1949, now Patent No. 2,823,615.

One of the means proposed for providing separate chambers between backfaces of the end plates and the adjacent end wall, which chambers aresubject to different fluid pressures and consequently provide differentforces acting on different regions of the back faces of the end platestending to move the end plates axially toward the rotatable gears, isdisclosed in the United States Patent No. 2,756,681 to Oliver. Thismeans comprises sealing means disposed radially on the end plates orbushings within the chamber defined by the back faces of the end platesand the adjacent end wall, thereby creating a plurality of isolatedchambers behind the end plates which are each subject to pressure fluidhaving different pressure values from that in the other chambers.

In all of the aforementioned types of pressure loaded end plates orbushings, each end plate is provided with a tubular, o-r stepped portionformed on the back face thereof. The tubular portion is received in acomplementary bore in the adjacent end wall or bores in a closedhousing, which bores, cooperating with a respective tubular portion,maintain coaxial alignment of the opposed pairs of end plates. Each endplate and tubular portion thereof is provided with a bore therethroughthat is utilized to receive and carry a journal of the adjacentrotatable gear. This present invention relates to pressure loaded endplates in which the back face of each end plate is not provided with theaforementioned tubular or stepped portion thereby eliminating anyprecision boring of the end Wall or housing to carry and maintain theopposed sets of end plates in coaxial alignment, and it is, therefore,such an object of this invention.

It is still another object of this invention to provide a pressureloaded axially movable end plate or bushing that has the maximumcross-sectional thickness thereof defined by the front and back facesthereof.

It is another object of this invention to provide a pressure loadedgear-type pump in which the pressure loaded end plate is provided withmeans to balance the forces of a pressure gradient condition existingacross the front face of the end plate.

It is another object of this invention to provide a pressure loadedgear-type pump in which the chamber between the axially movable endplates and the adjacent end wall is divided into separate chambers whichseparate chambers are each subject to pressurized fluids of differentpressure values to thereby balance the result of the pressure gradientcondition existing across the front faces of the end plates and maintaina pumping seal with the adjacent sides of the rotatable gears.

It is a further object of this invention to provide a pressure loadedgear-type pump Where the chamber formed between the adjacent axiallymovable end plates or bushings and the adjacent end wall is divided intoa plurality of chambers by sealing means disposed within a longitudinalrecess means formed in the back faces of the end plates which cooperatewith the adjacent end wall to thereby isolate the plurality of chambersfrom each other, the chambers each being subject to pressurized fluidsof different pressure values to thereby balance the result of thepressure gradient condition existing across the front faces of the endplates and maintain a pumping seal with the adjacent sides of therotatable gears.

A further object of this invention is to provide such a pressure loadedgear-type pump as recited in the above objects that is reversible inflow therethrough by the inlet and outlet of the pump being adapted tobe interchanged, one for the other.

Other objects, advantages, and uses of the present invention will beapparent from a reading of the following detailed description taken inconjunction with the drawing wherein:

FIGURE 1 is a fragmentary cross-sectional view of a pump incorporatingfeatures of this invention and having a pair of intermeshing rotatablegears therein taken on line 11 of FIGURE 2.

FIGURE 2 is an end view of FIGURE 1 taken on line 2-2 thereofillustrating the end plates or bushings according to one embodiment ofthis invention.

FIGURE 3 is an axial cross-sectional view of the gear pump in FIGURE 1taken on line 33 thereof.

FIGURE 4 is a fragmentary cross-sectional view illustrating anotherembodiment of the end plate sealing means of this invention.

FIGURE 5 illustrates a corrugated spring utilized in the end platesealing means disclosed in FIGURE 4.

FIGURE 6 is a fragmentary cross-sectional view of another embodiment ofthe sealing means of this invention.

FIGURE 7 is a fragmentary cross-sectional view taken on lines 7-7 ofFIGURE 8 illustrating still another embodiment of the pressure loadedaxially movable end plate or bushing of this invention.

FIGURE 8 is an end view showing of the end plate in FIGURE 7 taken online 8-8 thereof.

Reference is now made to FIGURES 1 to 3 of the drawing, wherein likereference numerals are used throughout to designate like parts,illustrating an intermeshing rotatable gear type pump incorporatingvarious features of this invention. The pump comprises a housing 10having a pair of parallel intersecting bores 11 and 12 passingtherethrough. A pair of end walls 13 and 1-4- are securely fastened tothe housing 10 by a plurality of beaded bolts 15 passing through the endwall 14, housing 10, and a portion of end wall 13 where the bolts 15 arethreadably attached thereto. The housing 10 is also provided with a pairof opposed bores 16 and 17 which interconnect perpendicularly therespective junctures of the bores 11 and 12 with the exterior of thehousing 10. These bores 16 and 17 are utilized respectively as an inletand an outlet for the pump and may be respectively connected to a sourceof supply by a supply line and a utilization system or return line inany well known manner.

A pair of rotatable gears 18 and 19 are disposed respectively in thebores 11 and 12 and are so arranged that they intermesh at the junctureof the bores 11 and 12. The gear 18 is provided with a pair of opposedcoaxial journals 2t} and 21 disposed respectively and centrally on theside faces 22 and 23 of the gear 18. The journals 29 and 21 may beformed integrally with the gear 18 or may be suitably fastened thereto.Further, the journals 2!) and 21 may be hollow, although not shown. Thelefthand journal 21 of the gear 18, as viewed in the drawing, passesthrough a bore 24 formed in an end plate or bushing 25, disposed betweenthe gear face 23 and end wall 13, and a corresponding coaxial bore 26formed in the end wall 13. The free end of the journal 21 is adapted tobe connected to and rotated by a source of power (not shown) in a mannerthat is well known in the art. The righthand journal 29 is disposedwithin a bore 27 formed in a bushing or end plate 28 disposed betweenthe side face 22 and the end wall 13. As can be seen, the bore 27 onlypasses through the side or front face 29 of the end plate 28 andterminates within the interior of the end plate 28 at 30.

The gear 19 is also provided with a pair of coarial and opposed journals31 and 32 fastened to or formed integrally with the respective sides 23and 22 of the gear 19. Journal 32 is carried by a lefthand end plate 33constructed similar to the adjacent end plate 25 and journal 31 iscarried by a righthand end plate 34 constructed similar to the adjacentend plate 28. The end of the lefthand journal 32 is received in acounterbore 35 formed in the end wall '13.

As can be seen, upon rotation of the journal 21, the gear 18,intermeshing with gear 19, drives gear 19 Whereby the rotating gears 18and .19 carry and force fluid from the inlet 16 to the outlet 17. Thegears 18 and 19 and the respective pairs of adjacent end plates 25, 33and 28, 34- are all disposed within the bores 11 and 12 of the housing10, which bores 11 and '12 together with the end walls 13 and 14 definea pumping chamber 36 through which the passage of fluid flows upon therotation of the gears 18 and 19.

Each end plate, 25, 33, 28, and 34 is formed with a flat chordal surface37 whereby the surface 37 of each end plate mates with the surface 37 ofthe respective adjacent end plate when assembled in the pump. In thismanner the end plates completely seal the pump chamber 36 therebetweenin the bores 11 and 12.

The end plates or bushings 28, 3d, 25, and 33 are different from the endplates utilized in normally constructed pressure loaded gear-type pumpsin that they have no tubular portions extending from the back facesthereof. Therefore, the maximum cross-sectional thickness of the endplates 28, 34, 25, and 33 is defined by the back and front facesthereof.

The adjacent pair of end plates 28 and 34 are so formed that the backfaces 38 thereof are spaced from the adjacent surface 39 of the end"wall 14 whereby a chamber is defined therebetween. End plates 28 and 34are adapted to be moved axially relative to the journals 20 and 31respectively within this chamber as the ends 40 of journals 20 and 34remain spaced from the ends 30 of the bores 27 even when the end platesare in their extreme left position.

In normally constructed pressure loaded gear-type pumps, this chamber isadapted to receive pressure fluid, the force of which tends to axiallymove the end plates 28 and 34 toward the left and cause the front faces29 thereof to engage the adjacent side faces 22 of the gears 18 and 19to form a pumping seal therewith. As previously mentioned, in normallyconstructed pressure loaded gear-type pumps a pressure gradientcondition exists across the front faces 29 of the end plates 23 and 34,the result of which tends to cause skewing of the end plates andsubsequent wearing of the front faces on the inlet sides thereof. Theelimination of this feature is one of the main purposes of thisinvention and the structure relating thereto will now be described.

The back faces-38 of the end plates 28 and 34 are each formed with aV-shaped recess 41 that extends substantially perpendicularly to theaxes of rotation of the gears 18 and 19 and divides the surface area ofthe combined back faces 38 into two substantiallyequal areas. Althoughthe recesses 41 have been described as V-shaped, any other configurationmay be utilized such as arcuately-shaped, etc. A pin 42 or othersuitable sealing means is disposed within the recess 41 throughout theentire cross-sectional length of bores 11 and 12 and divides the chamberbetween the back faces 38 and the end wall 14 into two separate chambers43 and 44.

Chamber 43 is adapted to be interconnected with the inlet side of thepump chamber 36 by means of a passage 45 formed in the housing 10 at thejuncture of bores '11 and 12 thereof. Similarly, chamber 44 isinterconnected with the outlet side of the pump chamber 36 by a passage46 formed in the housing 10.

The end walls 13 and 14 are suitably fluid sealed with respect to thehousing by O-ring seals and the journal 21 is suitably fluid sealed tothe end wall 13 by any well known pilot pressure loaded sealing meanssuch as is disclosed in the patent to Roth et a1. 2,420,622.

The operation of the pump is as follows: upon rotation of the gears 18and 19, by means of the rotation of journal 21 by a suitable powersource, fluid entering the inlet 16 is carried by the gears 18 and 19through the pump chamber 36 to the outlet 17. As the pressure value ofthe fluid carried by the gears 18 and 19 increases from the inlet 16 tothe outlet, the output pressure fluid delivered to chamber 44 by meansof passage 46 causes the pin 42 to be wedged between the sides of therecesses 41 and the surface 38 of the end wall 14 and thereby completelyisolates chamber 44 from chamber 43. The force of the pressure fluid inchamber 44 also tends to move the bushings 28 and 34 axially to the lefton the outlet side thereof whereby the front faces 29 thereof engage theadjacent side faces 22 of the gears 18 and 19 to provide a pumping sealtherewith. Chamber 43 receives inlet pressure fluid through passage 45whereby the force of the pressure fluid within chamber 43 also tends toaxially move the bushings 28 and 34 to the left on the inlet sidethereof. The combined forces acting on the back faces 38 overcome theforce of the pressure fluid within the pump chamber acting on the frontfaces 29 causing the end plates 28 and 34 to maintain the pumping sealthroughout the operation range of the pump.

As previously described, the fluid pressure within the chamber 36increases in value from the inlet 16 to the outlet 17 providing apressure gradient condition existing across the front faces 29 of thebushings 28 and 34. Because of this pressure gradient condition, thepressure fluid force action on portions of the front faces 29 adjacentthe inlet side thereof and tending to urge and axially move the endplates 28 and 34 to the right is a lesser value force than the value ofthe force of the pressure fluid adjacent the outlet tending to move theend plates 28 and 34 to the right. The forces provided by the pressurefluid in each chamber 43 and 44 imparted to regions adjacent the inletand outlet of the back faces 38 of the end plates 28 and 34 tending toaxially move the end plates 28 and 34 to the left is substantially equaland slightly greater than the opposing forces acting on the front faces29 adjacent the regions of chambers 43 and 44. As can be seen, the aboveconfiguration of the chambers 43 and 44 behind the end plates 28 and 34provides a balanced pressure loading thereof which eliminates anyskewing or tilting of the end plates due to the pressure gradientcondition existing across the front faces 29 thereof.

Should it be desired to reverse flow through the pump, all that isrequired is to change the direction of rotation of the power take offjournal 21, thereby making the outlet 17 an inlet and inlet 16 anoutlet. In this reversed arrangement the function of the chambers 43 and44 are now reversed whereby the inlet pressure fluid is directed tochamber 44 and theoutlet pressurefluid is directed to chamber 43, thepin 42 isolating the two chambers 43 and 44in the same manner heretoforedescribed.

' As can be seen, this invention provides a reversable pump of thepressure loaded type in which it is relatively simple to produce achange of direction of flow therethrough. This feature is not availablein normally constructed pressure loaded gear-type pumps of the typespreviously mentioned in which the tubularportion of the end plate isoffset or eccentrically mounted to compensate for the pressure gradientcondition existing across the front faces of the end plates. a a a Aspreviously stated, the recesses 41 could have any cross-sectionalconfiguration other than V-shaped, as

illustrated in FIGURES l to 3, and one such configuration may berectangular as shown in FIGURE 4. In the FIGURE 4 embodiment, arectangular recess 47 is formed in a pressure loadable-axially movableend plate 48. A pin 49 is disposed in the recess 47 separating the spacebetween the back face 50 of the bushing or end plate 48 and the adjacentside face 51 of the end wall 52 into chambers 53 and 54. A corrugatedspring 55 is disposed between the pin 49 and the bottom of the recess 47to initially preload the pin 49 against the surface 51 of the end wall52. This preloading of the pin 49 assures that when outlet pressurefluid is in chamber 53 or 54, whichever the case may be, the force ofthe higher pressure value fluid will act on a majority of the surface ofthe pin 49 to sufficiently cause wedging and a sealing thereof betweenthe end plate 48 and end wall 52. A side view of spring 55 isillustrated in FIGURE 5.

Another embodiment of the sealing means of this invention is disclosedin FIGURE 6 wherein the pressure loadable axially movable end plate 56is provided with a rectangularly-shaped recess 57. Disposed withinrecess 57 is a rectangular or square-shaped pin 58 which performs thesame function as pins 49 and 42 previously described. It should beunderstood that the particular cross-sectional configuration of thesealing means interposed between the end plates and the end wall is notcritical.

It is to be further understood that, although, as heretofore described,the recesses 41, 47, and 57 have been formed in the end plates 28 to 34,48, and 56 respectively, it is obvious that the recesses could be formedin the end wall instead to retain the sealing means. Further, both theend plates and adjacent end well could each be formed with a recess withthe same results. The essential purpose of the invention being toprovide some means for retaining a sealing means between the back facesof the end plates and the adjacent end wall to provide a plurality ofchambers therebetween.

Another embodiment of this invention is disclosed in FIGURES '7 and 8wherein a housing 10 is provided with a bore 59 having semi-circular endportions 60 and 61 and substantially parallel side portions 62 and 63tangentially connected to the end portions 60 and 61. Only one pressureloadable axially movable end plate 64 is required, it serving the samefunction as end plates 28 and 34 as disclosed in FIGURES l to 3. The'endplate 64 is adapted to be inserted within the bore 59 whereby the outerperiphery of the end plate 64 substantially fills the bore 59 at allpoints thereof throughout the crosssection of the end plate 64. A recess65 is formed throughout the entire length of the back face 66 of the endplate 64, dividing the back face 66 into two substantially equal areas.A pin 67 is disposed within the recess 65 dividing the space between theback face 66 and the adjacent side face 68 of the end wall 69 into twosub.- stantially equal chambers 70 and 71. Chambers 70 and 71 areutilized in the same manner as chambers 43 and 44 heretofore described.

The pump, as shown in FIGURE 8, may be provided with a conventionalinlet 72 formed in housing 10 and an outlet 73 also formed in housing ItIn the embodiment of the pump shown in FIGURE 7 the end wall 69 may beprovided with an inlet 74 and outlet 75 whereby the inlet 74 isinterconnected with chamber 70 and the outlet is interconnected with thechamber 71. In the latter form the end plate 64 is also provided withbores 76 and 77 formed therein interconnecting the respective chambers76 and 71 with the adjacent inlet and outlet sides of the pumpingchamber. In this manner fluid enters the pump through'inlet 74, fillchamber 70, and passes through bore 76 in the end plate 64 to thepumping chamber at a point where the interrneshing gears are separatingduring rotation, which gears carry the fluid around the pump chamber toa point where the gears begin to intermesh, discharging the fluidthrough 7 bore 77 in the end plate 64. The output pressure fluid passesfrom bore 77 into chamber 71 and from chamber 71 out through outlet 75.As can be seen, inlet pressure fluid is present in chamber 70 and outletpressure fluid is present in chamber 71 just as in chambers 43 and 44 ofFIGURES 1 to 3 and function in the same manner.

The intermeshing gear pump as disclosed in FIGURES 7 and 8 may also havethe flow of fluid reversed whereby the inlet 72 or 76 becomes an outletand the outlet 73 or 75 becomes an inlet. The sealing pin 67 serves thesame function regardless of the direction of fluid flow.

It is also to be understood that the pumps heretofore describedincorporating features of this invention could also serve as fluidmotors.

As can be seen, the pressure loaded gear-type pump disclosedincorporating features of this invention is relatively simple tomanufacture and provides a pump in which the end wall is not required tohave accurately machined bores therein to receive a portion of the endplates which would cause misalignment of the pump assembly ifinaccurately machined. Further, the axially movable end plates serve asthe sole supporting and carrying means for the journals of the rotatablegear members received therein. Therefore, a pump made in accordance withthis invention is less likely to fail due to misalignment of therotating gear assemblies.

Referring again to FIGURE 1, it should be noticed that chambers 78 areformed between the ends 4-0 of the journals and 31 and the ends 30 ofthe bores 27 in the end plates 28 and 34. The purpose of this clearancespace or chamber 78 is to permit the end plates 28 and 34 to be axiallymoved into engagement with the side faces 22 of the gears 18 and 19.Therefore, if any wear results on the front faces 29, there isadditional room for the end plates 28 and 34 to be axially moved towardthe left. If any of the fluid pressure within the pumping chamber 36should seep through bores 27 into chambers 78, suitable vents (notshown) could be provided eliminating any dash pot effect of chambers 78.One such vent could be formed by making the journals of the pumpingunits hollow, thereby permitting the chambers 78 to be ventedtherethrough to the inlet or atmosphere.

It should be further understood that the bores 11 and 12 in the housing10, as shown in FIGURE 2, could be substituted by a single bore such asis provided in FIGURE 8 by the bore 59 whereby the parallel sides of thesubstituted bore would serve the same function as the channels orpassages 45 and 46.

Heretofore the back faces of the axially movable end plates have beendescribed as being divided into only two substantially equal areas. Itshould be understood that the back faces could be divided into more thantwo areas in much the same manner as is disclosed in the aforementionedUnited States patent to Oliver 2,756,681 without departing from thescope of this invention. Further, the end plates and 32 could also bemade to be pressure operated and axially movable in the same manner asthe axially movable end plates disclosed by the patent to Oliver wherebythe journals 21 and 32 serve the same purpose as the tubular portions ofthe end plates described in that patent.

Where herein the various parts of this invention have been referred toas being located in a right or left position or moved to the right orleft, it will be understood that this is done solely for the purpose offacilitating the description and that such references relate only to therelative positions of the parts as shown in the accompanying drawing.

While this invention has been disclosed in connection with certainspecific embodiments thereof, it is to be understood that these are byway of example rather than limitation, and it is intended that theinvention be defined by the appended claims which should be given ascope as broad as consistent with the prior art.

What is claimed is:

l. A hydraulic apparatus comprising: a housing including means defininga chamber therein; means defining an inlet and an outlet in said housingleading respectively to and from said chamber; rotatable means disposedin said chamber for receiving liquid from said inlet and delivering thesame out through said outlet; bushing means disposed in said chamber forrotatably mounting said rotatable means therein and comprising opposedflat and axially spaced front and rear surf-aces defining the maximumradial thickness of said bushing means which extends continuouslythroughout its length, said chamber being continuous throughout itsength to substantially conform with said bushing means, said frontsurface being interrupted by cylindrical bore means for rotatablymounting said rotatable means and the remaining flat portion thereofbeing cooperable with adjacent side face means of said rotatable meansto provide a seal therewith, said bore means terminating within saidbushing means, said rear surface being spaced from and cooperable withan adjacent end wall of said chamber; means defining recess means in oneof said rear surface and said adjacent end wall; sealing means disposedin said recess means in sealing engagement with said rear surface andsaid cooperable adjacent end wall and effective to divide the spacetherebetween into a plurality of cavities, one of said cavities beingdisposed adjacent said inlet and in fluid communication therewith,another of said cavities being disposed adjacent said outlet and influid communication therewith whereby liquid from said inlet is suppliedto said one cavity and liquid from said outlet is supplied to saidanother cavity so that the force of the respective liquid acting on saidrear surface in the region of the respective cavity balances therespective opposition force acting on said front surface in the sameregion thereof and causes said bushing to cooperate with said rotatablemeans to provide said seal.

2. A hydraulic apparatus comprising: a housing including means defininga chamber therein; means defining an inlet and an outlet in said housingleading respectively to and from said chamber; a gear disposed in saidchamber for receiving liquid from said inlet and delivering the same outthrough said outlet, said gear having a fiat side and a journalextending therefrom; bushing means disposed in said chamber forrotatably mounting said gear therein and comprising opposed flat andaxially spaced front and back surfaces defining the maximum radialthickness of said bushing means which extend continuously throughout itslength, said chamber being continuous throughout its length tosubstantially conform with said bushing means, said front surface beinginterrupted by a cylindrical bore for receiving said journal and theremaining flat portion thereof being cooperable with said side face ofsaid gear to provide a seal therewith, said bore terminating in saidbushing means and permitting axial movement of said bushing meansrelative to said gear, said back surface being spaced from andcooperable with an adjacent end wall of said chamber; means defining arecess means in said back surface; pin means disposed in said recessmeans in sealing engagement with said back surface and said cooperableadjacent end wall and effective to divide the space therebetween intotwo substantially equal cavities, one of said cavities being adjacentsaid inlet and in fluid communication therewith, the other of saidcavities being adjacent said outlet and in fluid communication therewithwhereby liquid from said inlet is supplied to said one cavity and liquidfrom said outlet is supplied to said other cavity so that the force ofthe respective pressure liquid acting on said back bushing surface inthe region of the respective cavity balances the respective oppositionforce acting on said front bushing surface in the same region thereofand causes said bushing to cooperate with said gear to provide saidseal.

3. A hydraulic apparatus as recited in claim 2 wherein said recess meansin the back surface of said bushing'has a substantially V-shapedcross-sectional configuration.

4. A hydraulic apparatus as recited in claim 2 wherein said recess meansin the back surface of said bushing has a substantially arcuately-shapedcross-sectional configuration. v

5. A hydraulic apparatus as recited in claim 2 wherein said recess meansin the back surface of said bushing has a substantiallyrectangularly-shaped cross-sectional configuration.

6. A hydraulic apparatus comprising: a housing including means defininga chamber therein; means defining an inlet and an outlet in said housingleading respectively to and from said chamber; a pair of meshing gearsdisposed in said chamber for receiving liquid from said inlet anddelivering the same out through said outlet, said gears each having aflat side and a journal extending therefrom; bushing means disposed insaid chamber for rotatably mounting said gears therein and comprisingopposed substantially flat and axially spaced front and back surfacesdefining the maximum radial thickness of said bushing means whichextends continuously throughout its length, said chamber beingcontinuous throughout its length to substantially conform with saidbushing means, said front surface being interrupted by a pair ofcylindrical bores for respectively receiving said journals and theremaining flat portion thereof being cooperable with said side faces ofsaid gears to provide a seal therewith, said bores terminating withinsaid bushing means and permitting axial movement of said bushing meansrelative to said gears, said back surface being spaced from andcooperable with an adjacent end wall of said chamber; means definingrecess means in said back surface; sealing means disposed in said recessmeans in sealing engagement with said back surface and said cooperableadjacent end wall and effective to divide the space therebetween intotwo substantially equal cavities, one of said cavities being adjacentsaid inlet and in fluid engagement therewith, the other of said cavitiesbeing adjacent said outlet and in fluid communication therewith wherebyliquid from said inlet is supplied to said one cavity and liquid fromsaid outlet is supplied to said other cavity so that the force of therespective pressure liquid acting on said back bushing surface in theregion of the respective cavity balances the respective opposition forceacting on said front bushing surface in the same region thereof andcauses said bushing means to cooperate with said gears to provide saidseal.

7. A hydraulic apparatus comprising: a housing having an internalperipheral continuous and uninterrupted surface defining a chambertherein and a pair of end walls closing off said chamber; means definingan inlet and an outlet in said housing leading respectively to and fromsaid chamber; rotatable means disposed in said chamber for receivingfluid from said inlet and delivering the same out through said outlet;axially movable bushing means disposed in said housing for rotatablysupporting said rotatable means, said bushing means having flat frontand rear surfaces defining the maximum radial thickness of said bushingmeans which thickness is continuous throughout its length andsubstantially conforms to the peripheral surface of said chamber, saidfront surface being adapted to cooperate with said rotatable means toprovide a seal therewith, said rear surface be ing spaced from andcooperable with an adjacent end wall of said chamber; sealing meansdisposed between said rear surface and said adjacent end wall anddividing the space therebetween into a plurality of cavities,said-sealing means extending across said rear surface from a firstportion of said internal peripheral surface to another portion of saidinternal peripheral surface; and means for conveying pressure fluid toat least one of said cavities whereby the force of the fluid actsagainst said rear surface and causes said front surface to cooperatewith said rotatable means to provide said seal.

10 8. A hydraulic apparatus comprising: a housing having an internalperipheral'continuous and uninterrupted surface defining a chambertherein and a pair of end walls closing off said chamber; means definingan inlet and an outlet in said housing leading respectively to and fromsaid chamber; rotatable means disposed in said chamber for receivingfluid from said inlet and delivering the same out through said outlet;axially movable bushing means disposed in said housing for rotatablysupporting said rotatable means, said bushing means having fiat frontand rear surfaces defining the maximum radial thickness of said bushingmeans which thickness is continuous throughout its length andsubstantially conforms to the peripheral surface of said chamber, saidfront surface being adapted to cooperate with said rotatable means toprovide a seal therewith, said rear surface being spaced from andcooperable with an adjacent end Wall of said chamber; means definingrecess means in one of said rear surface and said adjacent end wall;sealing means disposed in said recess means and dividing the spacebetween said rear surface and said adjacent end wall into a plurality ofcavities, said sealing means extending from a portion of said internalperipheral surface to another portion of said peripheral surface; andmeans for conveying pressure fluid to at least one of said cavitieswhereby the force of the fluid acts against said rear surface and causessaid front surface to cooperate with said rotatable means to providesaid seal.

9. A hydraulic apparatus comprising: a housing hav ing an internalperipheral continuous and uninterrupted surface defining a chambertherein and a pair of end walls closing off said chamber, said chamberdefining an internal peri heral surface of said housing; means definingan inlet and an outlet in said housing leading respectively to and fromsaid chamber; rotatable means disposed in said chamber for receivingfluid from said inlet and delivering the same out through said outlet;axially movable bushing means disposed in said housing 'for rotatablysupporting said rotatable means, said bushing means having flat frontand rear surfaces, said bushing means further having a continuous anduninterrupted outer periphery to substantially conform with the internalperipheral surface of said chamber, said front surface being adapted tocooperate with said rotatable means to provide a seal therewith, saidrear surface being spaced from and cooperable with an adjacent end wallof said chamber; means defining recess means in one of said rear surfaceand said adjacent end wall, said recess means being disposedperpendicularly with respect to the axis of rotation of said rotatablemeans; sealing means disposed in said recess means dividing the spacebetween said rear surface and said adjacent end wall into a plurality ofcavities, said sealingmeans extending from a portion of said internalperipheral surface to another porhem of said peripheral surface; andmeans for conveying pressure fluid to at least one of said cavitieswhereby the force of the fluid acts against said rear surface and causessaid front surface to cooperate with said rotatable means to providesaid seal.

10. A hydraulic apparatus comprising: a housing having an internalperipheral continuous and uniniterrupted surface defining a chambertherein and a pair of end walls closing off said chamber, said chamberdefining an internal peripheral surface of said housing; means definingan inlet and an outlet in said housing leading respectively to and fromsaid chamber; a pair of intermeshing gears disposed in said chamber forreceiving fluid from said inlet and delivering the same out through saidoutlet; axially movable bushing means disposed in said housing forrotatably supporting said gears, said bushing means having flat frontand rear surfaces defining the maximum radial thickness of said bushingmeans which thickness is continuous throughout its length andsubstantially conforms to the peripheral surface of said chamber, saidfront surface being adapted to cooperate with said gears to provide aseal therewith, said rear surface being spaced from and cooperable withan adjacent end wall of said chamber; sealing means disposed betweensaid rear surface and said adjacent end Wall and dividing the spacetherebetween into a plurality of cavities, said sealing means extendingfrom a portion of said internal peripheral surface to another portion ofsaid peripheral surface; and means for conveying pressure fluid to atleast one of said cavities whereby the force of the fluid acts againstsaid rear surface and causes said front surface to cooperate with saidgears to provide said seal.

11. A hydraulic apparatus comprising: a housing having a pair ofparallel intersecting bores formed therein and a pair of end wallsclosing off said bores, said bores defining an internal peripheralcontinuous and uninterrupted surface of said housing; means defining aninlet and an outlet in said housing leading respectively to and fromsaid bores; a pair of intermeshing gears disposed respectively in saidbores for receiving fluid from said inlet and delivering the same outthrough said outlet; a pair of axially movable bushing means disposedrespectively in said bores for respectively rotatably supporting saidgears, said bushing means each having fiat front and rear surfacesdefining the maximum radial thickness of said bushing means whichthickness is continuous throughout its length and substantially conformsto the peripheral surface of said chamber, said front surface beingadapted to cooperate with an adjacent gear to provide a seal therewith,said rear surface being spaced from and cooperable with an adjacent endWall of said housing; sealing means disposed between said rear surfacesand said adjacent end wall and dividing the space therebetween into aplurality of cavities, said sealing means extending from a portion ofsaid internal peripheral surface defined by one of said bores to anotherportion of said peripheral surface defined by the other of said bores;and means for conveying pressure fluid to at least one of said cavitieswhereby the force of the fluid acts against said rear surfaces andcauses said front surfaces to cooperate with said gears to provide withseal.

References Cited in the file of this patent UNITED STATES PATENTS2,527,941 Lauck et al. Oct. 31, 19.50 2,707,44l Drennen May 3, 19552,714,856 Kane -1 Aug. 9, 1955 2,728,301 Lindberg Dec. 27, 19552,756,681 Oliver July 31, 1956 2,809,592 Miller et a1. Oct. 15, 19572,816,512 Murray Dec. 17, 1957 2,824,524 Banker Feb. 25, 1958 2,842,066Hilton July 8, 1958 FOREIGN PATENTS 706,979 Great Britain Apr. 7, 1954738,782 Great Britain Oct. 19, 1955 1,006,722 Germany Apr. 18, 19571,142,537 France Apr. 1, 1957

